It is known that safety barriers can be used along roads to prevent vehicles whose drivers have lost control from leaving the road.
However, the wide variety of vehicles traveling on the roads makes it necessary to resort to safety barriers, the restraining level of which is appropriate to the types of vehicle so that, on the one hand, a car or other lightweight vehicle will not be crushed against a barrier that is too rigid and on the other hand a truck or heavier vehicle does not cross the safety barrier.
In particular, in the event of a collision, the rail must be capable of restraining both a lightweight vehicle, the center of gravity of which is low to the ground, as well as a heavy vehicle, the center of gravity of which is much higher.
EP2 180 098 describes the use of a safety barrier comprising a spacer in the form of a bent tab, whereby the spacer comprises, from its lower end to its upper end, a first fastening area to the post, a first spacer area designed to move a portion of the spacer away from the post, a fastening area to the rail, a second spacing area and a second fastening area to the post in the form of a return leg of the tab downward, whereby this second fastening area is located in the plane of the first fastening area.
Each of the two fastening areas comprises a notch in the shape of an upside-down V at each of the ends of the spacer. The bolts that connect the spacer to the post are positioned in the throat of the V, in other words in the upper position of the indentation. When a vehicle strikes a safety barrier comprising the spacer and begins to bend a post, the spacer is at the same time driven downward by the post and is caused to remain in place by the set of rails of the safety barrier. The effect of these antagonistic forces is to make the bolts connecting the spacer to the post jump out of their notch, thereby releasing the spacer from the post. The rail thus released from the post prevents the vehicle from passing above the rail.
However, the solution proposed by EP2 180 098 has the disadvantage that it results in the detachment of the rail in the event of impacts by lightweight vehicles. Bolts, even when well tightened, have a very small surface area in contact with the notch and jump out of the notch as the result of minor impacts. The risk that a lightweight vehicle will pass underneath the rail is therefore high.
In addition, the time the rail is released from the post is controlled directly by the tightening torque of the bolts that connect the spacer to the post. However, the tightening torque varies as a function of the expansion of the materials, which are subject to climatic variables. This solution is therefore not very reliable because the rail risks being released from the post even by minor impacts and as a result of variable forces exerted on the safety barrier.
Finally, this solution is not compatible with the need to have safety barriers that have a good level of restraint both for lightweight vehicles and for heavy vehicles.